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SUMMARY:Real space calculation of response functions using non-diagonal su
 percells - Jonathan Lloyd-Williams (TCM)
DTSTART:20150617T104000Z
DTEND:20150617T110000Z
UID:TALK59839@talks.cam.ac.uk
CONTACT:Dr. Mike Towler
DESCRIPTION:We study the direct calculation of response functions using re
 al space methods. By considering supercell matrices with non-zero off-diag
 onal elements\, we show that it is possible to determine the response of a
  periodic system to a perturbation characterized by a wave vector with fra
 ctional coordinates k = ( m1/n1\, m2/n2\, m3/n3 )\, where m1/n1\, m2/n2\, 
 and m3/n3 are reduced fractions\, using a supercell containing l_123 primi
 tive\ncells\, where l_123 is the lowest common multiple of n1\, n2\, and n
 3. Utilizing such supercells facilitates the performance of real space fir
 st principles vibrational calculations using Brillouin zone grids of unpre
 cedented size. We calculate highly converged values of the zero-point reno
 rmalization to the thermal and optical band gaps of diamond arising from e
 lectron-phonon coupling. The use of non-diagonal supercell matrices enable
 s\nreal space methods to address problems that were previously only access
 ible to perturbative methods.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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